I spent research time today working through the first draft on a paper by Melissa Ness (MPIA) about the chemical homogeneity of clusters of stars. She is using very close stars in abundance space to look at what we can say about stars that are (and aren't) born together. I also spoke with Adrian Price-Whelan (Princeton) about marginalizing the likelihoods for our binary-star and not-binary-star hypotheses in Gaia DR1 TGAS. After some terrifying experiments over the weekend with numerical marginalizations, we decided that we have to bite the bullet and do the analytic marginalization, which requires completing the square. We both agreed to write down math.
At lunch time I gave the Brown-Bag talk at the CCPP. I spoke about Ness's work, and also about Price-Whelan's work. I see these things as related, because Ness finds stars that are clearly co-eval in chemical space, while Price-Whelan finds stars that are clearly co-eval in phase space.